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Subject[PATCH 2/2] ext4: update s_journal_inum if it changes after journal replay
Date
When mounting a crafted ext4 image, s_journal_inum may change after journal
replay, which is obviously unreasonable because we have successfully loaded
and replayed the journal through the old s_journal_inum. And the new
s_journal_inum bypasses some of the checks in ext4_get_journal(), which
may trigger a null pointer dereference problem. So if s_journal_inum
changes after the journal replay, we ignore the change, and rewrite the
current journal_inum to the superblock.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216541
Reported-by: Luís Henriques <lhenriques@suse.de>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
fs/ext4/super.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 260c1b3e3ef2..3fe9dc19ff9c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5953,8 +5953,11 @@ static int ext4_load_journal(struct super_block *sb,
if (!really_read_only && journal_devnum &&
journal_devnum != le32_to_cpu(es->s_journal_dev)) {
es->s_journal_dev = cpu_to_le32(journal_devnum);
-
- /* Make sure we flush the recovery flag to disk. */
+ ext4_commit_super(sb);
+ }
+ if (!really_read_only && journal_inum &&
+ journal_inum != le32_to_cpu(es->s_journal_inum)) {
+ es->s_journal_inum = cpu_to_le32(journal_inum);
ext4_commit_super(sb);
}

--
2.31.1
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